A significant advance has been made in the field of portable electronic devices, such as personal computers and cellular phones. For the portable electronic devices, there has been need of a chargeable power storage device having a high energy density, which is small, lightweight, and reliable. As such a power storage device, a lithium-ion secondary battery is known, for example. In addition, development of electrically propelled vehicles incorporating secondary batteries has rapidly advanced with a growing awareness to environmental problems and energy problems.
For a lithium-ion secondary battery, lithium metal oxide is used as a positive electrode material. The lithium metal oxide is a source of supply of lithium for the positive electrode.
Further, complete solidification of a lithium-ion secondary battery is under development (see Patent Document 1).